U.S. Pat. Nos. 5,036,256 and 5,051,665, which issued to Garrison et al and are assigned to the same assignee as the present invention, relate to circuits for starting and operating an HID lamp in a dc mode.
Although these circuits have been employed successfully, it has been found that certain disadvantages do exist which leave something to be desired. Since the voltage of a HID lamp can vary greatly from lamp to lamp both during warm up and during normal operation, a circuit that adjusts lamp power according to only the lamp voltage during warm up, cannot provide adequate performance.